1. Field of the Invention
The present invention relates generally to a composition and method for removing organic contaminants from solid substrates. More particularly, the present invention relates to a hydrogen peroxide composition for removing organic contaminants such as solder flux; and to a method of using this composition.
2. Description of the Background Art
In the fabrication of printed circuit boards, integrated circuits, and various electronic components and devices, solder is used to join various component metal parts together. The solder itself comprises an alloy, such as of zinc and copper or of tin and lead. Prior to application of the solder to the metal surface, the surface is treated with a fluxing agent to remove oxides and other contaminants which might interfere with the metal bonding, and to prevent reformation thereof during the solder process. These fluxing agents are typically organic materials such as natural rosin extracted from pine tree sap, organic acids such as carboxylic acid, hydrazines, amines and amides, or inorganic materials such as inorganic acids or salts. The most commonly used fluxing agent is acid rosin flux. The term "rosin flux" is used herein to mean a flux material which comprises rosin, i.e., the resin after distilling turpentine from the exudation of species of pine, and containing abietic acid and its anhydride. Typically, a small amount of another acid is added to rosin flux to activate it and such compositions are referred to as "acid rosin flux" or "activated rosin flux." After the solder operation has been completed, excess flux as well as flux residues remain on the soldered surface, and these residues are resinous, waxy and conductive. These flux residues and excess flux must be removed prior to subsequent processing steps in order to prevent reaction thereof with the bonded part, leading to corrosion and resultant electrical insulation losses.
Defluxing solvents which are widely used at present are halogenated hydrocarbons such as 1,1,1-trichloroethane and Freon (a tradename of E. I. DuPont for polyhalogenated hydrocarbons including chlorine and fluorine). While these organic materials are effective defluxing solvents, they have the serious disadvantage that they have a negative impact on the environment due to air pollution and ozone depletion. In fact, recent environmental legislation mandates that these materials be banned or their production severely restricted in the next few years. When these materials are used, even in small quantities, expensive management systems for transport, storage, use, and disposal and environmental protection equipment must be used to prevent air and water discharges. In addition, waste solvents require energy intensive regeneration operations for these materials.
While numerous aqueous cleaners are available which are viable degreasing solvents, none of these has been found to be effective as an electronic component defluxing solvent. In addition, the resulting organic laden aqueous solvents require further processing before disposal.
Thus, an urgent need exists in the electronics industry for a solvent which effectively removes organic flux residues while at the same time avoiding any negative environmental impact. Such a solvent would also be desirable for removing other organic materials from other substrates.